Role of nitric oxide in the synthesis of prostaglandin F2 alpha and progesterone during luteolysis in the rat

In the corpus luteum (CL) prostaglandin F-2 mu, (PGF(2 alpha)) is a luteoly tic agent. Nitric oxide (NO) is a messenger molecule capable of modulating diverse pathophysiological processes. Many of these functions are related w ith the female reproductive tract. The aim of the present study was to inve stigate the role of ovarian NO in PGF(2 alpha) production and in progestero ne synthesis during CL regression in the rat. By means of the intrabursa (i .b.) ovarian sac treatment of two competitive NO inhibitors, NG-monomethyl- L-arginine (L-NMMA; 1 mg/kg); N-W-Nitro-L-arginine methyl ester (L-NAME, 3 mg/kg) and sodium nitroprusside (SNP, 0.05 mg/kg) as a NO generator we foun d that NO, produced by the ovarian tissue during the last days (days 8 and 9) of CL development, acted by increasing PGF(2 alpha) production in the ov ary and diminishing seric progesterone levels leading to CL involution. We also postulated a positive feedback mechanism between PGF(2 alpha) and NO, to ensure luteal regression. Thus, we injected intraperitoneally (i.p.) a l uteolytic dose (3 mu g/kg) of a synthetic PGF(2 alpha) during the mid and l ate phase of CL development. The ovarian activity was evaluated. The result s confirmed our hypothesis; we did not see any effect in mid-stage of CL de velopment, while at a late stage enhancement of ovarian NOs activity was ob served in PGF(2 alpha)-inyected animals.